1. Field of the Invention
The present invention relates to a manifold reactor for an automobile and, more particularly, a manifold reactor having a reactor vessel which defines a reaction chamber for recombustion of combustible components contained in exhaust gases introduced therein, wherein said reactor is further designed to heat a riser portion of an intake manifold for better combustion of fuel air mixture.
2. Description of the Prior Art
To meet with the intensifying requirements for the purification of automobile exhaust gases, there have been proposed various kinds of exhaust gas purifying devices, one of which is a manifold reactor. The manifold reactor is a device to recombust harmful combustible components such as HC and CO contained in the exhaust gas delivered from an engine before it is discharged to the atmosphere. For this purpose, the manifold reactor incorporates a reaction chamber for the recombustion of the combustible components.
The reaction chamber must be of proper size so as to allow for the exhaust gas to stay therein for a time long enough to accomplish satisfactory recombustion of combustible components contained in the exhaust gas. Furthermore, the reaction chamber requires good heat insulation in order to maintain a temperature high enough to accomplish the recombustion of combustible components. In the case of a rich reactor which employs secondary air for recombustion, a structure suitable for high mixing of the secondary air and exhaust gas is required. Thus, there are various conditions to be considered for a proper design of the reaction chamber of a manifold reactor.
When a manifold reactor is employed in a cross flow type engine only for the purpose of purifying exhaust gas, it is relatively easy to design a manifold reactor in which the aforementioned conditions are satisfied. However, when a manifold reactor is mounted on the same side of a counterflow type engine together with an intake manifold, the manifold reactor is usually mounted below the intake manifold so as to heat a riser portion of the intake manifold for the purpose of preheating fuel air mixture delivered from a carbureter to effect better combustion thereof. In addition to the primary object of purifying exhaust gases, and, in this case, there has been a problem in that not only the structure of the manifold reactor becomes complicated but also the temperature of the exhaust gas in the reactor chamber lowers due to heat absorption by the riser portion to such an extent that recombustion of combustible components is sometimes impeded.
FIG. 3 in the accompanying drawing shows a typical example of a conventional manifold reactor of the abovementioned type. In FIG. 3, an intake manifold 21 connected to a body 20 of an engine forms a riser portion 23 below a carbureter 22. An exhaust gas inlet tube 24 connected to the body 20 is introduced into a reaction chamber 26 of a body or reactor vessel of manifold reactor generally shown by 25. The body 25 is formed with a riser port 27 at its upper portion, whereby the reaction chamber 26 communicates to a bottom wall of the riser portion 23 through said riser port. The body 25 of the manifold reactor is further formed with an exhaust gas outlet port 29 which communicates to an exhaust pipe 28. The exhaust port 29 opens to an internal space of the reaction chamber 26. At a lower portion of the reaction chamber 26 there is provided an upwardly curved deflector 30.
The exhaust gas discharged from the engine flows through the inlet port 24 and enters into the reaction chamber 26 as indicated by arrow headed lines, and begins recombustion in the reaction chamber. The gas is then diverted by the deflector 30 to flow toward the riser portion 23. The riser portion 23 absorbs heat from the exhaust gas and is heated up, whereby atomization of fuel air mixture flowing through the intake manifold 21 is accelerated. The gas which has been cooled by releasing heat flows further through a remaining path as shown by an arrow-headed line and is exhausted from the exhaust port 29. In a conventional structure of this kind, the heat loss suffered by the exhaust gas due to heat absorption by the riser portion 23 is relatively high, whereby the temperature of the exhaust gas substantially lowers sometimes beyond the limit required for recombustion of HC and CO. Furthermore, the serious defect in the conventional structure resides in that the abovementioned heat loss is caused before the exhaust gas introduced into the reaction chamber traverses a substantial part of the flow path afforded by the reaction chamber. If the temperature of exhaust gas has once lowered, the remaining flow path, even if it is long, does not effectively contribute to recombustion of combustible components. Therefore, the efficiency of the conventional reactor as shown in FIG. 3 is relatively low. Furthermore, in the conventional structure, the riser portion 23 can only receive a relatively small amount of heat from the exhaust gas because the temperature of gas has not yet been sufficiently raised by recombustion of combustible components before it reaches the riser portion and, accordingly, sufficient heat is not available for the riser portion at the time of starting up the engine when stronger heating is desirable for better combustion of fuel air mixture.